Preparation of esters of alpha, beta-dichloropropionic acid



Patented Sept. 30, 1952 OHLOBQPBOPIONIQACID i *WilliamQNey, Jr'.;"SomersetCenterQMass "signor .to'General Aniline &-Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application December 9,1950, i

I 'i Serial No. 201M090 4 was; (01. 26054.87

Thisinvention relates to the preparation: of

esters of a,o-dichloropropionic acid by chlorination of the corresponding esters of acrylic acid. I have found that preparation of a s-dichloropropionic acid esters by passing chlorine into. the corresponding acrylic ester, is. complicated. by side reactions resulting in the formation of dimers and other high-boiling byproducts whichprevent the recovery of the desired a,p.-d ichloro propionic ester in satisfactory yields. {The reaction is quite highly exothermic'so that.temperature control. is difficult. If .the temperature is allowed to rise spontaneously, very little e dichloropropionic ester is produced.

The preparation of. esters of p-dichloropro;

picnic acid by chlorinationof the corresponding esters 'of acrylic acid was'carried out heretofore in the presence of a solvent such as chloroform (U. S. Patent 2,320,034) or methanol (J. A. C. S. 62, pages 3495-3498). Separation of the reaction product from solvents such as chloroform or methanol is inconvenient and costly. Moreover, upon preparing methyl a,,8-dichloropropionate in methanol according to the directions in J. A. C. S. 62, page 3495, I was unable to obtain a product of satisfactory purity by fractional distillation of thereaction mixture. Namely, the

proplonic acid-can beproducedinrelatively high yields from the corresponding acrylic esters by treatment-with chlorine ln-the presence of a quantity-of water amounting to 1 to 8% of the weight of the acrylic ester initially employed. When..water. isaddedin theseamounts, the chlorinationcan be carried out at temperatures from 10 to 80 C. without substantial varia tion in the yield obtained. The presence, in addition to water, of chlorine addition catalysts suchasiodine, bromine-or rnercuric salts, produces nosubstantial improvement in yield, and insomecases causes slight. lowering of the yield. Polymerization inhibitors; are. advantageously employedto. prevent. polymerization of ,.the. acrylic ester used as the 'startingmateriah However,

except for this effect, they too have no substantial" effect uponfthe yield of a,fi-dichloropropionate when water is present in the amount specified above. Irradiation of the reaction mixture with diifused daylight has been found to have no substantial effect on the yield, and according- 1y, it is immaterial whether the reaction mixture is protected from, or exposed to, such radiation. The process in accordance with my-inyention thus involves passing chlorine into a liquid ester 7 of acrylic acid mixed with 1 to 8% of its weight fraction having the proper boiling range had an index of refraction (11. of 1.4493, while methyl s-dichloropropionatehas an index of refrac-,

tion of 1.45108.

.It has also been-proposed to procedure and fractional distillation of theprodnot to recover methyl afi-dichloropropionate yielded a fraction having a refractive. index approximating that'of the pure ester, but in a yield of'only"10% of theory. j

Chlorinating .methyl. acrylate withgaseous,

chlorine inJthe presence of polymerization .in-

hibitors,'chlorine addition catalysts such, as ,io'-

dine, bromine 'or mercuric su1fate',.and maintaining low temperatures, sometimes produces somewhat higher yields, but the results arelunreliable.

and the yields obtained are notof sufficient,mag-r nitude to render the process of interest forearm mercial operations. I

It is an object of. this invention toprovide-an improved process for the preparation of esters of a,fi-dichloropropionic [acid .by chlorination of r the corresponding. acrylic esters,= wherein-high.

yields of pureproduct can Joe-obtained able and eflicient manner.

I have discovered that esters of-as-dichloror g in a .relichlorinate methyl .acrylate at 0 C., employing bromine as a catalyst (U. S. Patent 2,195,712) Repetition of this of water.: The temperature is preferably maintained at 0 to 40 C., but can be permitted to rise as high as 80 C. without adverse effect upon the'reaction. Temperatures below 0 C. can like- ].wise be employed, but are generally unnecessary.

I have found, for example, that maintenance of temperatures from to 0 C. does not materially increase the yield of the desired esters.

The esters of acrylic acid which. can be chlorinated indaccordance with this invention are esters of. saturated. aliphatic, cycloaliphatic and araliphatic alcohols .suchias, forv example, the acrylic acid esters of methanol, ethanol, propanol,

isopropanol, butanol; pentanol, 'isoam'yl alcohol,

octyl, decyl, lauryl, palmityl and stearyl alcohols, cyclohexanol, methyl cyclohexanol and benzyl alcohol. In addition, acrylic esters of saturated polyhydric. alcohols such as glycol, glycerol, 1,4-

butanediolzand' thelike can besimilarly chlorinated. w

' The process in accordance with my invention is illustrated in the following examples, wherein parts and -'percenta'gesare' by: weight; 1

135,4 pets of: mm acrylatel containing 0.25

hydroquinone as a polymerization inhibitor,;and.

3 2.8 parts of water were agitated in a glass reaction vessel shaded' from light, and cooled with a solid Cor-acetone bath, and chlorine gas was bubbled into the liquid ester at such a rate as 4 EXAMPLE 4 A mixture was prepared consisting of methyl acrylate containing 0.25% of its Weight of hydroquinone and 1% of its weight of an aqueous to maintain the temperature at about 40 C. I, After 4 hours, unabsorbed chlorine was observed memunc sulfate somtlon preparedby .dl-ssolvmg condensing in the exhaust gas condenser cooled pains P ,mercunc sulfate and Parts of with solid CO2 and no further cooling was sulfuric acid in 40 parts of water. Chlorine was quired to mairitam the temperature of the bubbled through the reaction mixture while action mixture at 40 C. The reaction mixture mamPa'mmg temperature at untll was neutralized with calcium carbonate until no chlomne avsorptmn Was substant1auy complete' further evolution of CO2 occurred or with'aque Upon fractional distillation of the resulting reous sodium carbonate until the pH of the. mix-' actwn mixturfa' meihyl a'fi'dmhlompropionate ture was 4 to 5. The reaction mixturewas then was recovered m a meld of 37% of theory' subjected to steam distillation. The organic non EXAMPLE 5 aqueous portion of the distillate was separated from the aqueous condensate and fractionally To 100 parts of cyclohexylacrylate were added distilled at an absolute pressure of 10 mm. of 10 parts of hydroquinone, 3 parts of water and 1 mercury. A low boiling fraction collected at 45 part of bromine to serve as a chlorination accelto 58 C. had a lower index of refraction than erator. Chlorine was passed into the liquid mixmethyl a,;8-'dichloropropionate.- The principal ture while maintaining the temperature at 30 to fraction distilled at 58 to 60C. at the aforesaid 40 C. When chlorine absorp w s complete. pressure, and had an index of refraction (11 the reaction pro Was dried Over a y us of 1.4503 to 1.4505. It was substantially pure sodium sulfate, and fraction'ally distilled under methyl p-dichloropropionate. 26.4 parts therer du d p sur Cy xy afi-d p of were recovered, corresponding to a yield of pionate was recovered as a fraction boiling at 107 41% of theory, based on the methyl acrylate ini- C. at 4 mm. of mercury absolute pressure, in a tially employed, I yield comparable with those obtained in the fore- 1 I v I I going examples. EXAMPLE V As a comparison with the foregoing examples, I 100 parts of freshly distilled methyl acrylate methyl acrylate was chlorinated in the absence containing 1.5% of its weight of water was chloof water at different temperatures and with varirinated in a vessel equipped with a reflux conous additions of catalysts and polymerization indenser, by passing chlorine into the mixture as hibitors, and methyl a,p -dichloropropionate was fast as absorption could occur. The temperature separated from the resulting reaction mixture. rose rapidly to the boiling point of methyl acry- The temperature, added material, and yield in late (80 to 81 C.) and the condensed methyl terms of per cent of theory are given in the folacrylate vapor was refluxed to the reaction mixlowing table.

' Table Temperature I Polymerization 23392 Y. Id

. Control Value Inhlbltor 0861;? 19

' 1, 1182111111... (ca. 80-135") None Pemm5 Reflux+heatmg 80 to 162 14 Reflux.- (ca. 80-135) 11 (ca. 80-135") 14 -10 to 0 0. 19, (ca. 80435) d 16 (ca. 80135) 11 35 to 0 C. o d 11 0 C. 0.25% hydroquinone 10 ---35 C. 1% tert. butylcate- 21- ch01. 10C. do 0.1% I, 11

ture. When no further chlorine absorption occurred, the reaction mixture was allowed to cool and fractionally distilled under reduced pressure. 95 parts of methyl a,fi-dichloropropionate were thus recovered; having a boiling point of 65C. at an absolute pressure of 15 mm. of mercury, and an index of refraction (11. of 1.4510; The yield of methyl a,fl-dichloropropionate was. 52%

of theory.

' EXAMPLEB Y Gaseous chlorine was passed into pure methyl acrylate containing 0.25% of its weight of hydroquinone and 2% of its weight of water. The reaction temperature was maintained at 35 to 40 C. by cooling with an ice bath.- Whene chlorine' absorption was substantially complete, the reaction mixture was fractionally distilled under reduced pressure. Methyl a,,8-dichloropropionate was recovered in a yield amounting to 41% of theory. I x

Instead of the esters employed inthe examples,

other esters of acrylic acid, as enumerated in the discussion preceding the examples can be similarly converted to the corresponding ayi-dichloropropionic esters with high yields.

In carrying out the reaction, chlorine is advantageously introduced in gaseous form until absorption substantially ceases, asindicatd by an absence of the tendency ofthe temperature to rise despite discontinuanc iof cooling, and by thepassage of most of the chlorine through the liquid reaction mixture without absorption. The presence of polymerization inhibitors such as tertiary butyl catechol, hydroquinone or picric acid in amounts from 0.1 to 1.5% is advantageous to prevent polymerization of the acrylic esters undergoing treatment in the reaction mixture. Chlorine addition catalysts are of no substantial advantage and are preferably omitted. The temperature is advantageously maintained at 0 to 40 C. for uniformity of control, although temperatures from to 80 C. can be used without substantial disadvantage. The reaction product can be recovered from the mixture by fractional distillation under reduced pressure. If desired, steam distillation may precede the final fractional distillation. Fractions boiling at higher temperatures than the a,;9-dichloropropionic ester are generally found to contain chlorinated dimers and chlorinated higher polymers of the acrylic ester.

Variations and modifications which will be obvious to thoseskilled in the art can be made in the procedures hereinbefore described, without departing from the scope or spirit of the invention.

I claim:

1. A process for the preparation of an ester of a,p-dichloropropionic acid, which comprises passing chlorine into a liquid acrylic acid ester of an alcohol of the class consisting of saturated aliphatic, cycloaliphatic, and araliphatic alcohols,

containing from 1 to 8% of its weight of water.

2. A process for the preparation of an ester of a,p-dichloropropionic acid, which comprises passing chlorine into a liquid acrylic acid ester of an alcohol of the class consisting of saturated 'aliphatic, cycloaliphatlc, and araliphatic alcohols;

containing from 1 to 8% of its weight of water, at a temperature of 10 to 80 C.

3. A process for the preparation of an ester of 0.,5- dichloropropioni-c' acid, which comprises passing chlorine into a liquid. acrylic acid esterof an alcohol of the class consisting of saturated aliphatic, cycloaliphatic, and araliphatic alcohols, containing from, 1 to 8% of its weight of water, at a temperature of 0 to 40 C. until chlorine absorption is substantially complete, and recovering the a,fl-dichloropropiorlic acid ester from the reaction mixture.

4. A process for the preparation of methy1 41,13- dichloropropionate, which comprises passing chlorine into liquid methyl acrylate containing lto 8% of its weight of water at a temperature from -.10 to C., and recovering a,,3-dichloropropionate from the reaction products by frac-' tional distillation.

- WILLIAM O. NEY, JR.

N9 re e es ted! 

2. A PROCESS FOR THE PREPARATION OF AN ESTER OF A,B-DICHLOROPROPIONIC ACID, WHICH COMPRISES PASSING CHLORINE INTO A LIQUID ACRYLIC ACID ESTER OF AN ALCOHOL OF THE CLASS CONSISTING OF SATURATED ALIPHATIC, CYCLOALIPHATIC, AND ARALIPHATIC ALCOHOLS, CONTAINING FROM 1 TO 8% OF ITS WEIGHT OF WATER, AT A TEMPERATURE OF -10 TO 80* C. 